Banking or commercial transactions performed with cards, wherein the identification of the user is ensured by a card number and possibly confirmed by a secret code, are commonly used today. These cards can have a chip and/or a magnetic strip or other data storage means. They can even be virtual.
Protection by secret code normally ensures the identification of the user who, theoretically, is the only one who knows this code. But there are transactions in which a secret code cannot be used, particularly in telephone or minitel commerce.
There are several other possible protection methods, including biometrics (fingerprints, the iris of the eye, voice, etc.) but the secret code number is still the easiest to apply and is therefore the one that has been chosen for “consumer” transactions.
Unfortunately, it is still possible for a third party to learn the number of the card, for example during the transaction, when this number has to be communicated, and the secret code can still be detected during its entry, particularly at automated teller machines on the street. As a result, if the card is stolen, it is possible to use it and to perform transactions as long as the theft is not recorded in banks' computers.